JP2005066960A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drop droplets on a conveyance belt when a paper having a size smaller than a paper size set when a recording medium is conveyed using a conveyance belt, and the paper is soiled or the conveyance performance is deteriorated. .
A state detection sensor 41 for detecting the presence or absence of a sheet 12 on the operation line of the carriage 3 is provided on the downstream side of the carriage 3 in the main scanning direction, and the state detection sensor 41 is used when the carriage 3 performs main scanning for printing. By canceling the printing operation by the recording head 7 after detecting the absence of the sheet, droplets from the recording head 7 are prevented from landing on the conveying belt 21 outside the area of the sheet 12 fed.
[Selection] Figure 7

Description

  The present invention relates to an image forming apparatus.

  For example, an ink jet recording apparatus is known as an image forming apparatus (also referred to as an image recording apparatus) such as a printer, a facsimile machine, and a copying apparatus. The ink jet recording apparatus refers to a recording medium (hereinafter also referred to as “paper”, which is not limited to paper, but includes OHP, etc.), and can be attached to a droplet. (Also referred to as recording media, recording paper, etc.) Ink droplets are ejected to form a recording (image formation), which enables high-definition images to be recorded at high speed, low running costs, and noise. In addition, there is an advantage that it is easy to record a color image using multi-color ink.

  In such an ink jet recording apparatus, a recording head, which is a means for forming an image, is mounted on a carriage, the carriage is scanned, and an image is formed by conveying the recording medium. Information becomes important. By accurately acquiring the position information of the recording medium, recording start (image formation start) can be performed from an accurate position, and quality can be improved.

Here, conventionally, for example, there is a paper width sensor that is provided on a carriage to detect a suitable paper width according to the type of recording paper.
Japanese Unexamined Patent Publication No. 7-179248

In addition, there is an ink filling amount detection sensor in a waste ink storage unit that stores waste ink also used as a paper width detection sensor that detects the paper width of a recording medium.
JP-A-8-332738

In addition, a sensor for detecting the leading edge of the paper is provided on the upstream side in the paper conveyance direction of the feed roller that feeds the paper to the recording head, and a sensor for detecting the trailing edge of the paper is provided on the carriage on which the recording head is mounted. There is something.
JP 2001-10151 A

There is a paper sensor that detects the presence or absence of paper in the carriage, and this paper sensor is provided so as to detect the same position as the recording head in the paper transport direction, and detects the paper width direction and the paper trailing edge. .
JP-A-5-131729

In addition, a paper sensor for detecting the presence or absence of paper in the carriage is provided, and this paper sensor is provided so as to detect the same position as the recording head in the paper transport direction, and detects the paper width direction and the paper leading edge. is there.
Japanese Patent Publication No. 6-30933

Further, there is a paper sensor that detects a leading edge and / or a trailing edge of a sheet near the entrance of a conveyance roller that conveys the sheet.
JP 2002-265118 A

  As described above, in an image forming apparatus that records an image by ejecting liquid droplets, it is important to accurately obtain information on the recording medium to which the liquid droplets are attached, and in particular, the planar transportability of the recording medium is improved. For this reason, in an apparatus that transports a recording medium using a transport belt, if ink droplets are ejected from the recording head to a position off the recording medium, the ink droplets land on the transport belt, and the subsequent Troubles such as contamination of the back surface of the recording medium to be recorded and reduction in the adsorption power of the recording medium by the conveying belt occur.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus in which droplet discharge to a position outside a recording medium is suppressed as much as possible.

  An image forming apparatus according to the present invention includes a state detection unit for detecting the presence or absence of a recording medium on an operation line of the carriage on a carriage on which a recording head is mounted. The configuration is such that the subsequent printing operation is canceled when the detection means detects that there is no recording medium.

  Here, the state detecting means is provided on the main scanning direction side of the carriage, and in the main scanning for subsequent printing at the position without the recording medium by the state detecting means detected in the first main scanning for printing of the carriage. It is preferable to cancel the printing operation.

  Alternatively, it is preferable that the state detection unit is provided on the main scanning direction side of the carriage, and the printing operation is canceled by detecting the position where there is no recording medium by the state detection unit for each main scan for printing of the carriage.

  In these cases, the carriage is mounted with a plurality of recording heads that form an image by discharging droplets of a plurality of colors in the main scanning direction, and the carriage main scanning is performed even after the state detection means detects the absence of the recording medium. The printing operation is preferably canceled step by step for each recording head.

  At this time, control is performed to stepwise cancel the main scanning movement amount of the carriage and the printing operation of each recording head after the absence of the recording medium is detected based on the information regarding the adjustment value of the distance between the heads of the plurality of recording heads. It is preferable.

  In addition, the carriage is equipped with a recording head in which a plurality of nozzle arrays for forming an image by discharging droplets of a plurality of colors are arranged in the main scanning direction, and the carriage is detected even after the absence of a recording medium is detected by the state detection means. It is preferable to continue the main scanning and cancel the printing operation step by step for each nozzle row of the recording head.

  Furthermore, it is possible to print in both directions by moving the carriage in both directions, and when the printing operation is canceled in one direction printing, the printing operation is canceled in one direction printing in the other direction printing. It is preferable to cancel the printing operation for the area that has been printed.

  Alternatively, it is possible to perform printing in both directions by moving the carriage in both directions, and it is preferable that the state detection means is provided on both sides in the main scanning direction.

  The state detection means is provided on the upstream side of the carriage in the recording medium conveyance direction, starts scanning after the carriage is main-scanned and the end of the recording medium is detected by the state detection means, and the carriage main body for subsequent printing is started. It is preferable to detect the edge of the recording medium at the next main scanning position by the state detection means for each scanning.

  In this case, a plurality of recording heads for forming an image by discharging a plurality of color droplets are mounted on the carriage side by side in the main scanning direction, and the carriage main scanning is performed beyond the end of the recording medium detected by the state detection means. The printing operation is preferably canceled step by step for each recording head.

  At this time, it is preferable to perform control to cancel the main scanning movement amount of the carriage beyond the end of the recording medium and the printing operation of each recording head in a stepwise manner based on the information on the adjustment value of the inter-head distances of the plurality of recording heads. .

  Alternatively, the carriage is mounted with a recording head in which a plurality of nozzle rows that form an image by discharging droplets of a plurality of colors are arranged in the main scanning direction, beyond the end of the recording medium detected by the state detection means. It is preferable to continue the main scanning of the carriage and cancel the printing operation step by step for each nozzle row of the recording head.

  Further, it is preferable that the state detection means is provided at a position corresponding to the nozzle row at the end of the recording head in the main scanning direction of the recording head.

  These image forming apparatuses according to the present invention preferably include a conveyance belt that conveys the recording medium by electrostatic adsorption.

  According to the image forming apparatus of the present invention, since the subsequent printing operation is canceled when the absence of the recording medium is detected by the state detection unit during printing, it is possible to prevent droplets from adhering to other than the recording medium.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory side view for explaining the overall configuration of an ink jet recording apparatus showing an example of an image forming apparatus according to the present invention, FIG. 2 is an explanatory plan view of the main part of the recording apparatus, and FIG. It is explanatory drawing.

  In this ink jet recording apparatus, a carriage 3 is slidably held in a main scanning direction by a guide rod 1 and a guide rail 2, which are guide members horizontally mounted on left and right side plates (not shown), and a timing belt 5 is held by a main scanning motor 4. 2 is moved and scanned in the direction indicated by the arrow (main scanning direction) in FIG.

  The carriage 3 has a recording head 7 composed of four ink jet heads for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk), with a plurality of ink ejection openings. They are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward.

  As an ink jet head constituting the recording head 7, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like as an energy generating means for discharging ink can be used.

  Further, here, as shown in FIG. 4, a plurality (four in this example) each having a nozzle row 7a (which may be two or more rows) composed of a large number of nozzles N for discharging droplets of each color. ) Recording heads 7kh, 7ch, 7mh, 7yh are mounted on the carriage 3. As shown in FIG. 5, a plurality of nozzle rows 7kn, 7cn including a plurality of nozzles N for discharging liquid droplets of respective colors are provided. , 7 mn, 7 yn (not limited to four rows), a single recording head 7 may be provided.

  Further, the carriage 3 is equipped with sub-tanks 8 for the respective colors for supplying the inks of the respective colors to the recording head 7. Ink is supplied to the sub tank 8 from a main tank (ink cartridge) via an ink supply tube (not shown).

  On the other hand, as a paper feeding unit for feeding paper 12 stacked on a paper stacking unit (pressure plate) 11 such as a paper feed tray 10, a half-moon roller (for separating and feeding the paper 12 one by one from the paper stacking unit 11) A separation pad 14 made of a material having a large friction coefficient is provided facing the sheet feeding roller 13 and the sheet feeding roller 13, and the separation pad 14 is urged toward the sheet feeding roller 13 side.

  As a transport unit for transporting the paper 12 fed from the paper feed unit on the lower side of the recording head 7, a transport belt 21 for transporting the paper 12 by electrostatic adsorption, and a paper feed unit A counter roller 22 for transporting the paper 12 fed through the guide 15 between the transport belt 21 and the paper 12 fed substantially vertically upward is turned approximately 90 ° and copied onto the transport belt 21. A conveying guide 23 for adjusting the pressure and a tip pressing roller 25 urged toward the conveying belt 21 by a pressing member 24. In addition, a charging roller 26 as a charging unit for charging the surface of the transport belt 21 is provided.

  Here, the conveyance belt 21 is an endless belt, is stretched between the conveyance roller 27 and the tension roller 28, and the conveyance roller 27 rotates from the sub-scanning motor 31 via the timing belt 32 and the timing roller 33. By doing so, it is configured to circulate in the direction indicated by the arrow in FIG. 2 (belt (paper) conveyance direction: sub-scanning direction).

  This transport belt 21 is a surface layer that is a sheet adsorbing surface formed of a resin material having a pure thickness of about 40 μm that is not subjected to resistance control, for example, ETFE pure material, and resistance control by carbon is performed using the same material as the surface layer. It has a back layer (medium resistance layer, ground layer).

  Further, the conveyance roller nip portion 18 is formed by the conveyance roller 27 and the counter roller 22, and the sheet detection sensor 16 that detects the sheet 12 is disposed at a predetermined position upstream of the conveyance roller nip portion 18 in the sheet conveyance direction. . The paper detection sensor 16 detects the paper 12 by displacing the detection lever 17 by the paper 12 (the position indicated by the broken line in FIG. 1 is the ON position). The paper detection sensor 16 is for detecting paper feed.

  The charging roller 26 is disposed so as to contact the surface layer of the conveyor belt 21 and rotate following the rotation of the conveyor belt 21, and applies 2.5N to both ends of the shaft as a pressing force. Further, the transport roller 27 also serves as an earth roller, and is placed in contact with the middle resistance layer (back layer) of the transport belt 21 and is grounded.

  Further, a guide member 36 is disposed on the back side of the conveyance belt 21 so as to correspond to a printing area by the recording head 4. The upper surface of the guide member 36 protrudes toward the recording head 7 from the tangent line of the two rollers (the conveyance roller 27 and the tension roller 28) that support the conveyance belt 21. As a result, the conveying belt 21 is pushed up and guided on the upper surface of the guide member 36 in the printing region.

  As shown in FIG. 3, the carriage 3 has a state detection sensor 41 including a reflection type photosensor (optical sensor) that is a state detection unit for detecting the presence or absence of the paper 12 on the flow line of the carriage 3. Provided. The state detection sensor 41 is provided on the side positioned on the recording area (image forming area) side (conveying belt 21 side) when the carriage 3 is at the home position (the position indicated by the solid line in FIG. 3).

  Further, as shown in FIGS. 1 and 3, an encoder scale 42 having slits is provided on the front side of the carriage 3, and a transmission type photosensor that detects the slits of the encoder scale 42 is provided on the front side of the carriage 3. An encoder 44 for detecting the position of the carriage 3 in the main scanning direction (position with respect to the home position) is configured.

  Further, as a paper discharge unit for discharging the paper 12 recorded by the recording head 7, a separation unit for separating the paper 12 from the conveyance belt 21, a paper discharge roller 52 and a paper discharge roller 53, and paper discharge And a paper discharge tray 54 for stocking the paper 12 to be stored.

  A double-sided paper feeding unit 61 is detachably mounted on the back. The double-sided paper feeding unit 61 takes in the paper 12 returned by the reverse rotation of the transport belt 21, reverses it, and feeds it again between the counter roller 22 and the transport belt 21.

  Further, although not shown, a maintenance / recovery mechanism for maintaining and recovering the nozzle state of the recording head 7 is disposed in the non-printing area on both sides in the scanning direction of the carriage 3. The maintenance / recovery mechanism includes a cap member for capping the nozzle surface of the recording head 3 and a wiper blade for wiping the nozzle surface.

  In the ink jet recording apparatus configured as described above, the paper 12 is separated and fed one by one from the paper feed unit, and the paper 12 fed substantially vertically upward is guided by the guide 15, and includes the transport belt 21 and the counter roller 22. The leading end is guided by the conveying guide 23 and pressed against the conveying belt 21 by the leading end pressing roller 25, and the conveying direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately repeated from the high voltage power source to the charging roller 26 by a control circuit (not shown), that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 21 is alternating, that is, In the sub-scanning direction, which is the circumferential direction, plus and minus are alternately charged in a band shape with a predetermined width. When the paper 12 is fed onto the conveyance belt 21 charged alternately with plus and minus, the paper 12 is electrostatically attracted to the conveyance belt 21, and the paper 12 is moved in the sub-scanning direction by the circular movement of the conveyance belt 21. Be transported.

  As described above, the recording medium can be stably transported by transporting the recording medium by electrostatic attraction using an endless transport belt as the transporting means. In other words, the conveying means can be constituted by a roller such as a conveying roller, but in this case, since the contact area between the recording medium and the roller as the operation source is small, the conveying state tends to become unstable. On the other hand, since the contact area with the recording medium is increased by using the conveyance belt, the conveyance can be stabilized.

  Therefore, by driving the recording head 7 according to the image signal while moving the carriage 3, the ink droplets are ejected onto the stopped paper 12 to record one line, and after the paper 12 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 12 has reached the recording area, the recording operation is finished and the paper 12 is discharged onto the paper discharge tray 54.

  In the case of double-sided printing, when recording on the front surface (surface to be printed first) is completed, the recording belt 12 is fed into the double-sided paper feeding unit 61 by rotating the conveyor belt 21 in the reverse direction. The paper 12 is reversed (with the back surface being the printing surface), fed again between the counter roller 22 and the transport belt 21, controlled in timing, and transported onto the transport bell 21 as described above. Then, after recording on the back surface, the paper is discharged onto the paper discharge tray 54.

Next, an outline of the control unit of the ink jet recording apparatus will be described with reference to FIG. FIG. 6 is an overall block diagram of the control unit.
The control unit 80 includes a CPU 81 that controls the entire apparatus, a ROM 82 that stores programs executed by the CPU 81 and other fixed data, a RAM 83 that temporarily stores image data, and the like, while the apparatus is powered off. A non-volatile memory (NVRAM) 84 for holding data, an image processing for performing various signal processing and rearrangement on image data, an ASIC 85 for processing input / output signals for controlling the entire apparatus, and the host side An I / F 86 for transmitting and receiving data and signals, a head drive control unit 87 and a head driver 88 for driving and controlling the recording head 7, and a main scanning motor driving unit for driving the main scanning motor 4 89, a sub-scanning motor driving unit 90 for driving the sub-scanning motor 31, and the like.

  The control unit 80 is connected to an operation panel 91 for inputting and displaying information necessary for the apparatus, and further receives a detection signal from the state detection sensor 41 provided on the carriage 3. The

  The control unit 80 receives print data and the like from the host side such as an information processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera via the cable or the network via the I / F 86.

  The CPU 81 reads and analyzes the print data in the reception buffer included in the I / F 86, performs necessary image processing, data rearrangement processing, and the like in the ASIC 85, and transfers the image data to the head drive control unit 87. To do. The dot pattern data for image output may be generated by storing font data in the ROM 82, for example, or the image data is developed into bitmap data by a host-side printer driver and transferred to this apparatus. You may do it.

  When the head drive control unit 87 receives image data (dot pattern data) corresponding to one row of the recording head 7, the dot pattern data for one row is serialized to the head driver 88 in synchronization with the clock signal. Data is sent out, and a latch signal is sent to the head driver 88 at a predetermined timing.

  The head drive control unit 87 includes a ROM (which can be configured by the ROM 82) storing pattern data of a drive waveform (drive signal), and a D / A converter for D / A conversion of drive waveform data read from the ROM. A waveform generation circuit including an A converter and a drive waveform generation circuit including an amplifier and the like are included.

  In addition, the head driver 88 is a shift register that inputs a clock signal from the head drive control unit 87 and serial data that is image data, and a latch circuit that latches the register value of the shift register using a latch signal from the head drive control unit 87. A level conversion circuit (level shifter) that changes the output value of the latch circuit, an analog switch array (switch means) that is controlled to be turned on / off by the level shifter, and the like, and controls on / off of the analog switch array. In this way, a required drive waveform included in the drive waveform is selectively applied to the recording head 7 to drive the head.

Next, print control in this image forming apparatus will be described with reference to FIG.
First, the first embodiment will be described with reference to FIG. 7. Prior to paper feeding, the main scanning motor 4 is driven to rotate, and the carriage 3 at the non-recording position is moved to a substantially central portion (or a feeding portion) of the transport belt 21. The paper 12 is fed from the paper feed tray 10 after being positioned at a substantially central portion of the paper of the paper size to be printed.

  Then, the detection signal of the state detection sensor 41 is checked to determine whether or not the leading edge of the paper 12 has been detected, and the paper 12 is conveyed (fed) to a predetermined printing start position after the leading edge of the paper 12 is detected. Stop.

  Thereafter, the carriage 3 is temporarily returned to the home position, and the main scan to the recording area side of the carriage 3 is started based on the output of the encoder 44 with reference to the home position. Printing (printing operation) of the first (first) line (area printed by one scan of the carriage 3) is started.

  At this time, every time the carriage 3 moves by a predetermined amount, it is determined whether or not the printing (printing) of the line has been completed. If the printing of the line has not been completed, the detection signal of the state detection sensor 41 is checked. Whether or not there is a sheet 12 is determined.

  Here, if there is the paper 12, the scanning of the carriage 3 is continued and the printing of the line is continued.

  On the other hand, if there is no paper 12 (when the state detection sensor 41 detects no paper), the subsequent printing operation of the line is cancelled. Therefore, at this time, the print data of the line is cleared.

  Thereby, since printing (ink droplet ejection) is not performed at a place where the paper 12 is not present, ink droplets are not ejected onto the transport belt 21, and contamination of the transport belt 21 and the paper 12 can be prevented.

  Then, the remaining lines are printed with the width of the first line (width in the main scanning direction), and when printing of all lines is completed, the paper 12 is discharged if single-sided printing is performed. In the case of double-sided printing, the operation shifts to the operation of feeding the paper 12 to the double-sided unit 61, but the illustration is omitted.

  That is, as is the case with this image forming apparatus, the general operation method of the ink jet recording apparatus is to draw while moving the head H perpendicularly to the paper feed direction of the paper P as shown in FIG. An image is formed), drawing a constant width (one line) at the same time, and when drawing one line, the paper is moved, and drawing of a constant width is repeated to complete drawing of one sheet of paper.

  When drawing this one line, the position to which the carriage on which the head H is mounted should be moved based on the print setting information sent from the host.

  However, if the paper supply unit on the recording apparatus main body side does not have a paper size detection function, there is means for determining whether the paper size set on the host side is the same as the size of the paper actually fed. Therefore, as shown in FIG. 9, there is a possibility that paper P1 having a narrower width than the set paper P is fed.

  Further, as shown in FIG. 10, when the paper P is not fed in the correct state in the paper feeding process and is fed in an inclined state (paper P ′), the paper is fed to the original position. There is a possibility that the paper is not printed or the paper is torn. Further, a sheet having a distorted shape may be fed according to a user's request.

  In such a case, even if the paper is not at the position where the paper should be, printing is performed on the premise that the paper P of the size set by the print setting from the host is correctly fed. As shown in FIG. 9, printing (droplet ejection) is performed even at a position where there is no paper P1.

  If printing is performed at a position where there is no paper, if ink droplets adhere to the transport belt, the transport belt will be stained with ink, and the ink on the belt will move to the paper when the next paper is fed. Or the ink may adhere to all the working parts in the main body that are in contact with the belt, causing the life of the apparatus to be shortened. In addition, since printing is performed at a position where it is not necessary, ink is wasted, and ink is wasted.

  Therefore, in the present invention, a state detection sensor for detecting the presence or absence of a sheet on the carriage flow line is mounted on the carriage, and the sheet that has been fed has a width equal to or greater than the sheet set in the print settings. If there is no paper left in the middle of printing one line, it is assumed that the paper size set in the print settings matches the size of the fed paper, Follow the instructions.

  On the other hand, as shown in FIG. 11, if the sheet P1 runs out on the way, the subsequent printing operation for the line is canceled at that time, and the process proceeds to printing of the next line.

  In this case, assuming that the paper is correctly fed, the remaining lines are printed within the width of the first line in the main scanning direction, so the paper is fed diagonally. However, it is not possible to deal with a case where the paper is deformed or deformed, but it is not necessary to check the detection signal of the state detection sensor for each line (each scan), and the processing becomes simple.

  Next, a second embodiment of print control will be described with reference to FIG. Here, processing up to canceling the printing operation when the absence of paper is detected during printing of one line will be described.

  In this example, as shown in FIG. 4 described above, the four recording heads 7kh, 7ch, 7mh, and 7yh are arranged on the carriage 3 with the head-to-head distance x. 7yh is arranged at a distance a, the head 7yh is first in the main scanning direction (printing direction) of the carriage, similarly, the head 7mh is second, the head 7ch is third, and the head 7kh is fourth. To do. When viewed in the main scanning direction, the head 7yh is on the most downstream side and the head 7kh is on the most upstream side.

  As shown in FIG. 12, when the state detection sensor 41 detects that there is no sheet in the middle of printing one line, the main scanning of the carriage 3 is continued for the distance a. At this time, the four heads 7yh, 7mh, 7ch , 7kh is used to continue printing.

  Then, from the position where the carriage 3 is main-scanned by the distance a, the printing operation is canceled for the first head 7yh, and the second to fourth heads 7mh, Printing continues using 7ch and 7kh.

  Further, similarly, the printing operation is canceled for the first and second heads 7yh and 7mh, and the printing using the third and fourth heads 7ch and 7kh is continued while performing the main scanning of the carriage 3 by the distance x. To do. Similarly, the printing operation is canceled for the first, second, and third heads 7yh, 7mh, and 7ch, and printing using the fourth head 7kh is continued while scanning the carriage 3 by the distance x. Thereafter, the printing operation of the fourth head 7kh is canceled.

  That is, as shown in FIG. 13, when the printing operation is canceled when the state detection sensor 41 detects the absence of paper, the four heads 7yh, 7mh, 7ch, and 7kh are aligned in the main scanning direction. Since the timing of droplet ejection with respect to the dot position is deviated, a dot to which a necessary color droplet does not adhere is formed.

  Therefore, the distance between the state detection sensor 41 and the first head 7yh and the distance corresponding to the distances between the heads 7yh, 7mh, 7ch, and 7k continue to be printed by the head facing the paper. By canceling the printing operation step by step for a plurality of heads while continuing scanning, the necessary ink droplets can be ejected for all the dots, and the necessary ink droplets can be ejected to the edge of the paper. As shown in FIG. 14, an image can be accurately formed up to the end of the paper P. When a blank is provided at the edge of the paper, the printing operation of the first head is canceled when the state detection sensor 41 detects the absence of paper, and the subsequent heads are stepwise while continuing main scanning thereafter. The printing operation may be canceled.

  In the case of a head having a plurality of nozzle rows that eject droplets of different colors as shown in FIG. 5, the distance b between the state detection sensor 41 and the first nozzle row 7yn, and between the nozzle rows Processing similar to that in FIG. 12 may be performed using the distance xa.

  In this case, it is assumed that the four heads 7yh, 7mh, 7ch, and 7kh are arranged at a predetermined inter-head distance x in the main scanning direction, but in practice the inter-head distance is not constant, It is slightly different from device to device or changes over time. For example, FIG. 15 shows an example in which the distances between the heads of four heads 7yh, 7mh, 7ch, and 7kh are different from x, y, and z, respectively.

  For this reason, the inter-head distance adjustment value (difference with respect to the reference value) for adjusting the inter-head distance or the inter-head distance itself is stored and held as information (for example, stored in the aforementioned NVRAM or ROM) and the adjustment value. By controlling the amount of main scanning movement of the carriage 3 after the absence of paper and the cancellation of the stepwise printing operation for a plurality of heads, droplets are accurately placed at the same dot position by each of the plurality of heads. It is possible to print by landing.

  By applying the adjusted adjustment value of the distance between the heads to specify the position when the paper width is canceled and canceled, all colors can be accurately printed to the last edge of the paper. It becomes possible.

Next, the case of performing bidirectional printing as a third embodiment of print control will be described with reference to FIG.
In the bidirectional printing, the carriage 3 is moved in both directions to perform printing in both the forward path and the backward path. Therefore, printing is not performed in an area where there is no paper even during the backward path printing.

  For example, as shown in FIG. 16, when printing is performed by scanning the carriage 3 (recording head 7) on the forward path to the position indicated by the broken line and then printing the next line on the backward path, a plurality of four heads are printed. Printing is started from the head that has moved to a position where the paper P1 is located among 7yh, 7mh, 7ch, and 7kh. At this time, the print data corresponding to the area where the printing operation is canceled on the forward path after the sheet P1 is removed is canceled as the non-printable data, so that the area where the sheet is removed is not printed even during the return path printing. It is possible to correctly print on paper by bidirectional printing.

  As described above, in the area where the printing operation is canceled in the forward path, the bidirectional printing can be correctly performed within a certain range by canceling the printing in the backward path.

Next, a fourth embodiment of print control will be described with reference to FIG.
Here, in the same manner as in the first embodiment, when printing (printing operation) is started, it is determined whether or not printing (printing) of the line is completed each time the carriage 3 moves by a predetermined amount. If the printing is not finished, the detection signal of the state detection sensor 41 is checked to determine whether or not the paper 12 is present.

  If the sheet 12 is present, the main scanning (scanning) of the carriage 3 is continued and the printing of the line is continued.

  On the other hand, if there is no paper 12 (when the state detection sensor 41 detects that there is no paper), the printing operation for the line is canceled, and then the next line is printed. At this time, even during printing of the next line (printing of the line), the detection signal of the state detection sensor 41 is checked to determine whether or not the paper 12 is present. Process to cancel.

  That is, here, the detection signal of the state detection sensor 41 is checked for each line to determine whether or not there is the paper 12, and if there is no paper 12, the subsequent printing operation is canceled for that line. ing.

  In other words, if you check the width of the paper when it is fed, you can determine whether the paper is the same size as the paper set in the print settings, but the shape of the paper is distorted, If the paper is being fed diagonally, the position of the edge of the paper may be different from the position when it is fed while printing. Then, there is a risk of printing in an area protruding from the paper.

  Therefore, when the state detection sensor is positioned on the front side of the carriage in the traveling direction, by constantly monitoring the edge of the paper while printing, as shown in FIG. 18, each line always prints at the edge of the paper, Since the printing operation for the previous print data is cancelled, as shown in FIG. 19, the printing does not protrude from the paper.

  In the case of performing bidirectional printing, as shown in FIG. 20, by providing state detection sensors 41 and 41 on both sides of the carriage 3 in the main scanning direction, it is a line that is printed in either the forward path or the backward path. Also, the edge of the paper can be detected, and this embodiment can be applied.

Next, another embodiment of the image forming apparatus according to the present invention will be described with reference to FIG.
In the above-described embodiment, the state detection sensor 41, which is a state detection unit, is provided on the main scanning direction side of the carriage 3, but in this embodiment, as shown in FIG. A state detection sensor 41 which is a state detection means is provided. The head may have a configuration in which a plurality of nozzle rows shown in FIG. 5 are arranged.

  The print control in this case will be described with reference to FIG. 22. After the paper feed and leading edge detection are performed in the same manner as in the above embodiment, the carriage 3 is main-scanned and the state detection sensor 41 before starting printing. To detect the width of the paper 12.

  Thereafter, printing is started, and the printing operation after the detection of the absence of paper is canceled within the area of the width in the main scanning direction of the paper 12 detected by the recording head 7 while performing the main scanning of the carriage 3. While printing. At this time, the width of the sheet 12 is detected based on the detection result of the state detection sensor 41 for the line next to the line being printed (the line to be printed by the next main scanning of the carriage 3).

  Then, after the printing of the line is completed, the process proceeds to the printing of the next line. Similarly, the paper width of the next line of the line being printed is detected, and all the lines (one sheet of printing) are completed. Until this time, printing is performed while canceling the printing operation in the area outside the paper width.

  As a result, even when one state detection unit is provided, in bidirectional printing, printing can be performed while canceling the printing operation after no paper for each main scanning of the carriage.

  That is, when one state detection unit is provided on the main scanning direction side as described above, printing is performed while the carriage moves in the forward direction (the direction in which the state detection sensor moves forward in the main scanning direction). The state detection sensor can detect the edge of the paper before the head, but the state detection sensor moves behind the head when printing in the return direction of bidirectional printing. The printing operation cannot be canceled based on the detection result of the detection sensor.

  Therefore, by providing a state detection sensor upstream of the carriage in the paper conveyance direction, the paper width of the line next to the line being printed is monitored, and when the next line is printed, the previous line is printed. Printing is performed according to the width of the paper obtained at times. In this way, by monitoring the paper width of the line following the line to be printed, as shown in FIG. 23, even in bidirectional printing, printing can be performed while monitoring the paper width for all lines. .

  In this embodiment as well, the printing operation after detecting the edge of the sheet is canceled by the same recording head or nozzle row when the recording heads or nozzle rows are arranged in the main scanning direction as described above. Until the printing at the dot positions is completed, the main scanning of the carriage can be continued, and the printing operations of a plurality of recording heads or nozzle rows can be canceled in stages.

  Further, as shown in FIG. 24, a state detection sensor which is a state detection unit at a position corresponding to the recording head (or nozzle row) at the upstream side in the main scanning direction of the carriage 3 and on the upstream side of the carriage 3 in the sheet conveyance direction. If 41 is provided, the edge of the paper can be detected while printing the first line, and there is no need to perform a pre-scan to detect the width of the paper before the start of printing.

1 is a configuration diagram showing an outline of a mechanism part of an ink jet recording apparatus as an embodiment of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the mechanism part. It is a principal part schematic perspective explanatory drawing of the mechanism part. It is explanatory drawing explaining an example of the recording head mounted in the apparatus. It is explanatory drawing explaining the other example of the recording head mounted in the apparatus. It is a schematic block explanatory drawing of the control part of the same apparatus. It is a flowchart with which it uses for description of 1st Embodiment of the printing control of the same apparatus. It is explanatory drawing with which it uses for operation | movement description of the same embodiment. It is explanatory drawing with which it uses for operation | movement description of the same embodiment similarly. It is explanatory drawing with which it uses for operation | movement description of the same embodiment similarly. It is explanatory drawing with which it uses for operation | movement description of the same embodiment similarly. It is a flowchart with which it uses for description of 2nd Embodiment of the printing control of the same apparatus. It is explanatory drawing with which it uses for operation | movement description of the same embodiment. It is explanatory drawing with which it uses for operation | movement description of the same embodiment similarly. It is explanatory drawing with which it uses for operation | movement description of the same embodiment similarly. FIG. 3 is an explanatory diagram for explaining bidirectional printing control of the apparatus. It is a flowchart with which it uses for description of 3rd Embodiment of the printing control of the same apparatus. It is explanatory drawing with which it uses for operation | movement description of the same embodiment. It is explanatory drawing with which it uses for operation | movement description of the same embodiment similarly. It is explanatory drawing with which it uses for description of the other example of the same embodiment similarly. It is explanatory drawing with which it uses for description of other embodiment of the image forming apparatus which concerns on this invention. 3 is a flow for explaining printing control of the apparatus. FIG. 6 is an explanatory diagram for explaining the printing control. It is explanatory drawing with which it uses for description of the other example of the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Carriage 4 ... Main scanning motor 7 ... Recording head 12 ... Paper (recording medium)
21 ... Conveying belt 41 ... State detection sensor

Claims (14)

  In an image forming apparatus provided with a state detection means for detecting the presence or absence of the recording medium on an operation line of the carriage on a carriage mounted with a recording head for forming an image by discharging droplets onto the recording medium An image forming apparatus for canceling a subsequent printing operation when the state detection unit detects the absence of a recording medium when performing printing while performing main scanning on the carriage.   The image forming apparatus according to claim 1, wherein the state detection unit is provided on a main scanning direction side of the carriage, and there is no recording medium by the state detection unit detected in the first main scanning for printing of the carriage. An image forming apparatus that cancels the printing operation in the main scanning for subsequent printing at the position.   The image forming apparatus according to claim 1, wherein the state detection unit is provided on a main scanning direction side of the carriage, and the state detection unit detects a position without a recording medium for each main scanning for printing of the carriage. And canceling the printing operation.   4. The image forming apparatus according to claim 2, wherein a plurality of recording heads for forming an image by discharging droplets of a plurality of colors are arranged side by side in the main scanning direction on the carriage, and the recording medium by the state detection unit is provided. An image forming apparatus characterized in that main scanning of the carriage is continued even after the absence is detected, and the printing operation is canceled step by step for each recording head.   5. The image forming apparatus according to claim 4, wherein the main scanning movement amount of the carriage and the printing of each recording head after the absence of a recording medium is detected based on the information on the adjustment value of the inter-head distances of the plurality of recording heads. An image forming apparatus that performs control to cancel operation in stages.   4. The image forming apparatus according to claim 2, wherein the carriage is mounted with a recording head in which a plurality of nozzle arrays that form an image by discharging liquid droplets of a plurality of colors are arranged in the main scanning direction. An image forming apparatus characterized in that the main scanning of the carriage is continued even after the absence of a recording medium is detected by the detecting means, and the printing operation is canceled step by step for each nozzle row of the recording head.   7. The image forming apparatus according to claim 2, wherein the carriage can be moved in both directions to perform printing in both directions, and the printing operation is canceled in one-way printing. An image forming apparatus that cancels a printing operation for an area in which the printing operation is canceled in the one-way printing during printing in the other direction.   7. The image forming apparatus according to claim 2, wherein the carriage can be moved in both directions to perform printing in both directions, and the state detection unit is provided on both sides of the main scanning direction. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the state detection unit is provided upstream of the carriage in the recording medium conveyance direction, and after the carriage is main-scanned and the end of the recording medium is detected by the state detection unit, printing is performed. And an end of the recording medium at the next main scanning position is detected by the state detecting means for each main scanning of the carriage for subsequent printing.   10. The image forming apparatus according to claim 9, wherein a plurality of recording heads for forming an image by discharging droplets of a plurality of colors are arranged side by side in the main scanning direction on the carriage, and the recording detected by the state detection unit. An image forming apparatus, wherein main scanning of the carriage is continued beyond the edge of the medium, and printing operation is canceled step by step for each recording head.   11. The image forming apparatus according to claim 10, wherein the main scanning movement amount of the carriage beyond the end of the recording medium and the printing operation of each recording head are stepped on the basis of the information on the adjustment value of the distance between the plurality of recording heads. An image forming apparatus characterized by performing control to cancel automatically.   10. The image forming apparatus according to claim 9, wherein the carriage includes a recording head in which a plurality of nozzle arrays for forming an image by discharging droplets of a plurality of colors are arranged in the main scanning direction, and the state detection unit An image forming apparatus characterized in that main scanning of the carriage is continued beyond the edge of the recording medium detected in step 1, and the printing operation is canceled step by step for each nozzle row of the recording head.   13. The image forming apparatus according to claim 9, wherein the state detection unit is provided at a position corresponding to a nozzle row at an end of the recording head in a main scanning direction of the recording head. An image forming apparatus. 14. The image forming apparatus according to claim 1, further comprising a transport belt that electrostatically attracts and transports the recording medium.

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